Pressure-relief device



May 15, 1928 1,669,700

v C. C. EGBERT PRESSURE RELIEF DEVICE Filed May 4, 1923 )2 V52)? T0)" I W Patented May 15, 1928.

, CHARLES o. EGBERT, or NIAGARA FALLS, nEwYoRx.

PRESSURE-RELIEF DEVICE. I A

Application filed May 4, 1923. Serial No. 636,586.

My invention relates generally to safety devices, in the nature of bursting plates, used to relieve the pressure within any receptacle, and more particularly to a device for use in connection with penstocks supplying water for driving turbines.

It is well known to those skilled in the art, that prior to my invention of a pressurerelief device, for which I obtained Letters 1 Patent of the United States of America, No. 1,39%,072 on October 18, 1921, bursting plates used in pressure-relief devices had to be constructed with a very small factor of safety in order to be effective as ameans of relieving pressure. The experience was that the pulsations in pressure which usually occur in a penstock following sudden variations in the quantity of water discharged from the turbine supplied by the penstock, weakened a bursting plate, having a low factor of safety,

to such a degree that it burst unexpectedly at a lower pressure than that which it was designed to sustain. That is,-it burst under ordinary operating conditions with attending loss of service, and the expense and annoyance in'replacing broken parts.

The principal object of my invention has been to provide a pressure-relief device which will overcome the objections above set forth, and one which will have a suflicient factor of safety to insure againstbursting under ordinary conditions of service, but one which will give way at the predetermined excessive pressure, and thereby relieve the penstoc'l: of dangerous stresses which will be produced by the unrelieved" pressure-surge or water-hammen 1 Another object has been to provide a pressure-relief device, having a plurality of closing an opening in a receptacle, the-plates being so arranged that the fluid pressure in the receptacle is divided between them, one plate sustaining the pulsating pressure and the other plate sustaining a substantially constant pressure which is not materially in excess of the normal pressure until the predetermined bursting pressure has been reached.

Furthermore. I have sought to provide a device, which is simple and inexpensive to construct and maintain, and also one which is certain in its operation.

The above objects and advantages have been accomplished by the device shown in the accompanying drawings, of which:

bursting plates supplementing each other in Fig. 1 is a verticahsectional view of my complete device.

Fig. 2 18 a fragmentary view showing a modified means of securing the bursting plate in position.

Fig. 31s a fragmentary view of another modified form of my invention.

In this specification, I will describe my in- I vention as applied to a penstock supplying water toa turbine, it being obvious thatthe device is applicable to any receptacle carrying fluid under pressure. v

In the draw ings,5'represents the nozzleor branch of a penstock having the usual flange 6. A- ring .7, having an inwardly extending flange 8 and'an outwardly extending flange 9, 1s secured to the flange 6 by means .of a

plurality of bolts 10.' A stopper plate 11 is and is provided arranged within the ring 7 with an extension 12 and with a flange 13. The extension '12 is fitted into the inwardly extending flange 8 of the ring 7 so as to have sliding engagement therewith. The stopper plate 11 is held in position by means of a plurality of bolts 14, which pass through the flange 13 of the plate, and into the in- Each of these wardly extending flange 8. bolts is provided with a flattened portion 15, whereby it may be screwed into and out of the flange 8 by means of a wrench. Each of the bolts is provided between the flattened portion 15 and the outward end with a reduced portion 16 of predetermined crosssection.

Arranged adjacent the ring 7 is a bursting plate 17 This plate is preferably pro vided-with a flange 18, which is arranged adprcent and secured to the outwardly extending flange 9 of the ring 7 by means of a plurality 6r bolts 19. An equalizer ring 20 is preferably employed when high pressures are met, and this is arranged adjacent the flange 18, and is also held'in place by the bolts 19. The bursting plate 17 is provided-preferably on each side with an annular groove or score 21, so as to give to the plate'a' predetermined thickness at a point between the grooves, whereby it will have a predetermined bursting strength equal to the load imposed upon it by the predeter- The grooves 21 'are preferably larger in diameter than the mined bursting pressure.

flange l3 of'the stopper platell, whereby the stopper plate 11 will'be free to pass through the opening formed by the burstin plate'17 when it has been ruptured.

The stopper plate 11 is provided with an outwardly extending projection 22. This projection is carried at the center of the plate 11 and is, therefore, disposed opposite the center of the bursting plateli, andhas a small clearance space 23 between its outer end and the plate'17. The clearance 231s preferably made just large enough to perbursting plate 17. This aperture thus proofilluid to pass from the pjenstock to the- I show the use of bolts YltIlES a passageway for a limited quantity spaceilti. An aperture 2? is provided in the ring 7, and secured therein is'an automatic pressure relief valve 28. This valve is a standard article of commercial manufacture, and need not, therefore,-bedescribed in detail in this specification, except to state that it is of a type which will automatically discharge when a predetermined pressure is reached or exceeded. Therelief valve preferably has sufficientdischarge capacity to prevent the water, which enters the space 26 through the aperture 25 and by leakage I around the extension 12 of the stopper plate 11, from exceeding the predetermined maximum pressure in the space. The maximum pressure in the space 14 is preferably substantially the normal fluid pressure in the penstock branch 5.

In the form of invcntion shown in Fig. 2, 30 for holding the bursting plate 31 in position. These bolts are preferably reduced at 32 so as to have a predeterminedarea. In this form, the bolts will break when the predetermined pressure-is reached, instead of the plate as in the form above described.

The modification shown in Fig. 3 shows a stopper plate 33, which is secured to the flange 8 of the ring 7 by means of bolts 34 of I uniform diameter.

stopper plate 33 is provided with "a groove I when the penstock or score-'35xpreferably on each side thereof and in, opposite arrangement, whereby the plate is strength. In this form, theliursting plate 17 isthe samev asthe bursting plate in the form shown in Fig. 1, and it is preferably held in position by means of solid b olts..19.

It will be clear from the foregoing that v branch 5 is filled with waterpthe water will flow through the aperture, 25 into the space 26. Some wa er may also leakin at the joint between the extension 1.2 and the inwardly extending flange 8 of the ring '7, but this'will flow into the space 26 and a limited amount of leakage at this p i will n t be r mentalest-he v ditional load will 'In this form, the

given a predetermined bursting will rise to a point not] more than the pressure atwh'ich the relief valve 28 is set to discharge, which is a pressure preferably at substantially the normal pressure exlsting in the pcnstock branch 5. Under these con- 'ditions', as long as the boltsltremain intact, the water pressure within the space 26 will never exceed'the predetermined pressure at which the valve 28 is set to discharge.

By this arrangement, the burstingvplate 17 is protected from pulsating pressures,-and

will be-stcadily loaded at not exceeding practically normal pressure untilthepredetermined bursting pressure, is suddenly thrown upon it. lVhen, however, the predetermined bursting pressure in the penstock 5 is reached, the bolts 14 will break and the stopperplate 11' will be-forced toward the bursting plate 17 with the result that the load, carried by the bolts let and the stopper plate 11 will, be suddenlyimposed upon the bursting plate 17,

of the stopper plate 11, whereby the branch 5 will be opened, allowing an unobstructed discharge of water from the penstock, thus quickly relieving the excessive pressure therein. v.

It will be evident that when the bolts 14 break, the load sustained by them will be transferred to the bursting plate 17in either or both of two ways; namely, hydraulically, and mechanically. It will be movement of the stopper platell. toward the bursting'plate 17-will increasethe fluid pressure within the space 26, unless the re lief valve has a'capacity suflicient to instantly discharge-the water in volume equal to the displacement, and thusprevent its risingin pressure; However, if the fluid pressure in;

space 26 does rise," this risein pressure will act uponthe bursting plate 17, and such ad'- be equally distributed over the'area'of t-heplate 17. On the other hand,

when the stopper plate 11 moves'toward the bursting plate 17, and the projection 22 of the stopper plate contacts withthe'bursti'ng plate, the load upon the stopper plate will be directed and concentrated *uponthe center of the bursting plate 17,- except such part of theload as may as above explained. of the stopper plate -11 extends into the flange 8- a greater distance thanthc clearance space 23.,itis clear that the load carried by the stopper plate will be mechanically transferred, through the projection 22 to the bursting plate 17 before the pressure within the penstock is transferred to the bursting plate. A

Because of the construction above'pointed out, my device has agreater factor of safety than'if the bursting plate 17 were exposed to the surges occurring in the penstock since,

causing it to. burst, and opening the way for the e ection clear that any be transferred hydraulically, Since the extension 12 as is Well known, a given load when concentrated at the center of a platerequires that the plate be thicker and stronger than if the same load is distributed over the entire surface of the plate.

As hereinbefore pointed out, the factor of safety of my device is comparatively high. This may be clearly understood by assuming that; for instance, the normal pressure of the water in the penstock is 100; that under ordinary operating conditions, the water pressure frequently surges to 125; and that the bursting pressure of the device is 150. In such a case, the relief valve 28 is set to dis charge when the pressure in the space 26 exceeds 100. As long as the penstock pres sure is 100 or less, thepressure. in the space 26 will be the same, being equalized by the discharge of the water through the aperture 25 in either direction. When the pressure .in the penstock exceeds 100, the pressure in the space 26 tends to rise, as the water enters it through the aperture 25 and through the joint between the extension 12 and the flange 8. The pressure in the space 26 is, however, held at substantially 100 by discharge through the relief valve '28. The load thus imposed upon the bolts 14 is substantially equal to the area of the extension 12 multiplied by the difference of the unit pressures on the two sides of the stopper plate 11.

plate 11 is transferred mechanically to the plate 17 at its center. The bursting plate 17 may thus be made strong enough, as herein pointed out, to have a factor of safety of 2 or more depending upon the pressure surges. In other words, my device may be made strong enough so as to safely stand-with a factor of safety of 2 or morethe ordinary pressure surges of approxin'iately 125 (assuming the normal pressure to be 100) with the assurance that it will operate when the predetermined pressure of 150 is'reached. Comparing the factor of safety assured by my device with the ordinary single plate which is designed to burst at the same predetermined pressure of 150, it will be seen that the factor of safety in my device is much higher, Assuming the same pressures in the single plate design, this plate design would only have a factor of safety of 1.2 since 150 divided by the ordinary surge of 125 equals 1.2, while the factor of safety of to function, another one would act. over, the end of the extension 22 may be my device, as above pointed out, is 2 or more. Aside from the advantagesof my device, as just pointed out, the bursting plate 17 is steadily loaded while the bolts. 14 holding the stopper plate 11 take all of the pressure of pulsations, in simple tension, ordinarily occurring at frequent intervals in a penstock. l or'this reason, the bolts 14 of my device will sustain such pulsations with I have shown but one aperture for conduct ing fluid to the space 26, it is obvious that other apertures may be made through the through the stopper plate 11. Furthermore, if desired, a number of pressure-relief valves may be employed so that if one should fail Moremade pointed, if desired, and a cast-iron bursting plate may be made of reduced crosssection at its center so that it may be easily punctured by the extension. These and other modifications of the details herein shown and described may be made Without departing from the spirit of my invention orthe scope of the appended claims, and, therefore, I do not wish to be limited to the exact embodiment of the form herein shown and described, the form being merely a preferred embodiment thereof.

Having thus described my invention what I claim is: V j

1. The combination with a receptacle containing fluid under pressure, of a pressurerelief device characterized .by having a bursting" plate, a slidably mounted stopper plate disposed behind. the bursting plate and flange 8, or one or more apertures may be made i formed with a pistonportion and a central projection pointing toward the center of the bursting plate, one plate supplementing the other in retaining the fluid pressure in the receptacle until a predetermined pressure is reached.-when both plates give way allowing a free passage forthe discharge of fluid from the receptacle. 1

2. The combination with a receptacle, of a pressure-relief device characterizedby having a bursting plate, a slidably mounted stopper plate formed with a piston portion and with a central projection pointing toward the center of the bursting plate, the burstingplate being exposed to the normal fluid pressure existing within the receptacle. and means for counterbalancing the fluid pressure within the receptacle on the stopper, plate.

3. The combination witha receptaclefot a pressure relief device characterized by ha-v.

ing 'a bursting plate of predetermined strength, exposed to the normal fluid pressure existing within the receptacle, a. slidtaining fluid under pressizire, of apressure relief device characterized by having a bursting plate, a slidably mounted stopper plate in intcrspaced relation with the bursting plate, the stopper plate being formed with a piston portion and with a central projection pointing towardthe bursting plate, a fluid passageway between the interior of the receptacle and the space between the plates, and means for controlling the fluid pressure in the space, whereby one plate will supplement the other plate in retaining the fluid.

5. The combination with a receptacle containing fluid under pressure, of apressurerelief device characterized by having a bursting plate, a slidably mounted stopper plate disposed behind the bursting plate and having a central projectionpointing toward the center of the bursting plate and in interspaced relation therewith, the plates supplementin each other in retaining the fluid pressure in the receptacle until a predetermined pressure is reached, whereby when the stopper plate gives Way, the-pressure in the receptacle is thrown upon the center of the bursting plate.

6. The combination with a receptacle containing fluidunder pressure, of a pressurereliet device characterized by having a bursting plate, a slidablymounted stopper plate formed with a. piston portion, a convfined space between them afluid passageway between the interior of the receptacle and the spacebetween the plates,,each plate supplementing the other in retaining the fluid pressure in the receptacle, and means for controlling the fluid pressure in the space until a predetermined pressure in the receptacle is reached, whereby whenthe stopper plate gives way, the pressure in the receptacle thrown upon-the bursting plate.

7. The combination with a receptacle containing fluid under pressure, of a pressurereliei device 7 characterized by having a bursting plate, a stopper plate arranged behind the bursting-plate and slidably dis posed inthe receptacle, the stopper plate also having a central projection pointingtoward the center of the bursting plate and in interspaeed relation therewith, the plates supplementing each other in retaining the flu d pressure in the receptacle until a preably mounted stopper plate formed with a determined pressure is'- reached, whereby when the stopper plate gives way, the pressure in thereceptacle is thrown-"upon the centerof the bursting plate. V

8. The combination iwlth' a receptacle containing'fluid under pressure, the receptacle being formed with an, (emergency outlet opening, of i a pressure-reliefdevice characterized by having a burstingplate, a slidpiston portion which is mounted in the eme'rgcncy opening, the stopper plate being rela tively smaller than the bursting plate and disposed behind and in inter-spacedrelation with the bursting plate, one plate supplementing the other in maintaining the'fluid pressure in the receptacle until the pre- 1 determined pressure is reached, when one plate is burst and the other forced out of the emergency outlet openings 19. Thercomblnatlon wltha receptacleconraining fluid under pressure, the receptacle being formed with an emergency "outlet openinggrot a pressure-relief ,devicecharacterized by having a 'burstmg plate, a sl1d-' ablyimounted stopperplate formed with a piston portion which is mounted in the emergency opening, the stopperplate being relatively smaller than the bursting plate and disposedbehind and in intersp'aced rela tion with the bursting plate, the bursting plate being exposed to the normal fluid pressure existing within the receptacle; and means for.- .counterbalancing the fluid pressure within the receptacle on the stopper plate; I 1

10; The combination with a receptacle containing fluid under pressure, the receptacle being formed with tin-emergency outletopening,.ofa pressure-relief device eharacterized by having a bursting plate oi predetermined strength, a slidably m'ount'ed stopper plate formed with a piston portion which is mounted in the emergency opening, the stopper plate being relatively smaller than the bursting plate and-disposed behind and ininterspaced relation withfthe burst ing plate, bolts of predetermined strength for holding the stopper plate in place, the

bursting plate being exposed tothe'no'rmal fluid pressure existingwithin the receptacle, and means for counterbalan'cing the fluid pressure within. the receptacle on thestopper plate. 7 11,. The combination with receptacle containing fluidzunder pressure, tliereceplot;

tacle being formed with an eniergencyoutlet opening. of a pressure-reliefdevice characterized by having a burstin -plate, a slid ably mounted stopperplate; rormed with a piston portion mounted within the emer gency opening and witha central projection pointing towardthe center ofthe bursting plate,- the' stopper plate being relatively smaller than the burstingplate and disposed in i behind the bursting plate with its central projection in interspaced relation With the bursting plate, one plate supplementing the other in maintaining the fluid pressure in the receptacle until the predetermined pressure is reached when one plate is burst and the other plate is forced out of the emergency outlet opening.

12. The combination with a receptacle containing fluid under pressure, the receptacle being formed with an emergency outlet opening, of a pressure-relief device char- 7 acterized by having a bursting plate, a slid-v ably mounted stopper plate formed with a piston portion mounted with the emergency opening and With a central projection pointing toward the center of the bursting plate, the stopper plate being relatively smaller than the bursting plate and disposed behind the bursting plate with its central projection in interspaced relation With the bursting plate, the bursting plate being exposed to the normal fluid pressure existing within the receptacle, and means for counterbalancing the fluid pressure Within the receptacle on the stopper plate.

In testimony whereof, I have hereunto signed my name.

CHARLES C. EGBERT. 

